Scholars predict that the high court will avoid making a sweeping ruling on par with landmark civil rights decisions of the past

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The U.S. Supreme Court is wading into the same-sex marriage issue for the first time.

Updated at 11:46 AM EDT on Saturday, Dec 8, 2012

The U.S. Supreme Court made a historic decision when it chose Friday to address same-sex marriage, but the potential outcomes aren't as simple as deciding whether such unions are legal.

The high court could use California's Proposition 8 and the Defense of Marriage Act to issue broad decisions that would make it unconstitutional to block same-sex marriages or deny federal benefits to gay spouses. The court could also do the opposite and say such bans are not unlawful, and deal a considerable blow to the gay rights movement.

But legal scholars say the more likely scenario is a set of narrow rulings that support gay marriage but stop short of the kind of grand rulings of the past that settled matters of racial and gender discrimination.

"I think they will likely take the approach that would bite off the least ground," said Geoffrey Stone, a University of Chicago law professor and Supreme Court expert.

The options in each case vary widely.

On Proposition 8, the court could either uphold or reject California voters' 2008 ban on same-sex marriages -- passed in response to a state Supreme Court ruling that legalized gay marriage. But the court actually has four options, legal scholars say:

It could issue a far-reaching decision that declares that the Constitution protects same-sex marriages, thus invalidating similar bans in dozens of states around the country and allowing gay marriages to take place anywhere, said David Cruz, a University of Southern California law professor who specializes in civil rights and equality issues. This would uphold the decision by a federal judge who struck down Prop. 8 under the Constitution's equal protection clause.

The high court could rule that same-sex couples don't enjoy the same constitutional protections to marriage that opposite-sex couples do. That would keep Proposition 8 on the books, and essentially protect similar measures from being challenged elsewhere, Cruz said.

The justices could also rule that it was wrong for California to strip rights that had already existed, strike it down on those grounds, and leave it at that -- mirroring the narrow decision of the 9th U.S. Circuit Court of Appeals.

It could also rule that the sponsors of Prop. 8 did not have proper legal standing to make its case. This would likely send the case backwards through the court system to the original trial court, Cruz said. The overturning of Prop. 8 would probably stand, but the decision wouldn't have any legal influence on cases outside of California.

Then there's the DOMA case, one of several challenges to the 1996 federal law that defined marriage as between a man and a woman. The legislation prohibits same-sex couples in states that have legalized gay marriage from an array of federal benefits, including tax deductions, Social Security survivor benefits and federal employee health insurance.

Several married gay people have challenged DOMA on grounds they were denied assistance they would have otherwise had access to if they were in a heterosexual union. Several of those cases reached the Supreme Court's doorstep this year, but the justices agreed on Friday to take just one, and put off announcements on the others.

Under President Obama, the Justice Department has stopped defending DOMA in court, and the Republican-led House of Representatives has taken up the fight.

The case before the high court involves 83-year-old Edith Windsor, a New York woman who married her longtime partner, Thea Spyer, in 2007 in Canada. Spyer died two years later, and left Windsor her entire estate. Because of DOMA, Windsor could not seek tax exemptions for the inheritance, leaving her with a $363,000 tax bill.

Again, the Supreme Court has a range of options. It could uphold DOMA as constitutional, which many legal scholars see as unlikely. Or the the justices could rule against DOMA and choose to apply one of several tiers of legal scrutiny, depending on how unfair it deems the ban on same-sex marriage. Which level of scrutiny they choose would influence the breadth of the ruling's impact, Cruz said.

The DOMA and Prop. 8 cases are expected to be argued in March and decided in June. As for the other DOMA challenges, they probably won't be denied, just delayed until after the court rules on these two cases, Cruz said.

American public opinion has shifted gradually toward a more lenient view of same-sex marriage in the years since DOMA, and since Proposition 8. On Election Day this year, voters in Maine, Maryland and Washington endorsed gay marriages, bringing to nine the number of states where they are legal (the District of Columbia also allows them).

In May, President Barack Obama said his feelings on the issue had evolved to the point that he was comfortable with same-sex marriage.